Although there are several types of bright lenses having a photographing view angle of about 40 to 90 degrees and an F-number of about 3.5 or less for an interchangeable lens camera system, Gaussian-type lenses are widely known (refer to JP-A-6-337348 and JP-A-2009-58651). In the Gauss-type lens, the whole lens system or a part of lens group is moved in the optical axis direction when focusing is performed. In addition, other than the Gauss-type lens, a lens system has been proposed in which a first lens group having positive refractive power and a second lens group having negative refractive power are included, and the first lens group is moved in the optical axis direction when focusing is performed (for example, refer to JP-A-2009-210910).